High phase order electrical rotating machine with distributed windings

ABSTRACT

A rotating induction machine, containing five or more different phases, having windings distributed according to a sinc function with a cutoff frequency allowing low-order spatial harmonics but preventing higher order spatial harmonics from flowing. In a preferred embodiment, the machine is connected to drive means capable of injecting third harmonic into the machine. In a further preferred embodiment, the windings are connected to the drive means with a mesh connection and the machine has five phases.

CROSS-REFERENCE TO RELATED APPLICATION

This application is the U.S. national stage application of InternationalApplication PCT/US03/10346, filed Apr. 3, 2003, which internationalapplication was published on Oct. 16, 2003, as International PublicationWO03085801 in the English language. The International Application claimsthe benefit of U.S. Provisional Application No. 60/370,484, filed Apr.3, 2002. The above-mentioned patent applications are assigned to theassignee of the present application and are herein incorporated in theirentirety by reference.

TECHNICAL FIELD

The present invention relates to winding distributions in rotatingelectrical machines.

BACKGROUND ART

Previously disclosed, in U.S. Pat. Nos. 6,570,361 and 6,351,095, havebeen High Phase Order electrical rotating machine designs. Of specificinterest is the application “HIGH PHASE ORDER MOTOR WITH MESH CONNECTEDWINDINGS,” Ser. No. 09/713,654, filed Nov. 15, 2000, now U.S. Pat. No.6,657,334, which discloses the use of a high phase order concentratedwinding machine, connected to an inverter using a mesh connection. Whenusing a mesh connection, the voltage across each winding is a functionrelated to the voltages of both of the two inverter legs that drive thatwinding, and therefore, may be different from the actual voltagesproduced by the inverter legs. That machine is deliberately operatedeither with a fundamental drive waveform, a pure harmonic drivewaveform, or admixtures of these, in order to change the volts/hertzratio of an induction machine, in order to increase the power deliveredto the machine by a power electronics drive system when the motor wasbeing operated at low speed and thus reduced slot voltage. In otherwords, the motor can be operated at higher current than the currentsproduced in the inverter.

In my previously disclosed machines, extensive use was made ofconcentrated windings. Concentrated windings place inductors of a singlephase in a single slot in each pole of a stator. Motor windings areusually produced using coils of wire, with the portion of a coilresiding in one slot forming the inductors for that slot, and theportion of the same coil on the opposite side of the coil is placed inanother slot, forming a set of inductors with reverse polarity from thefirst. These two slots are placed 180 electrical degrees apart, formingso-called full span concentrated windings.

Concentrated windings offer numerous benefits, including the ability touse harmonic components of drive currents to produce useable rotatingfields, reduction in chording and distribution factors, which reduceresistance losses, and the ability to use specific harmonic drivewaveforms to obtain desired changes in machine impedance. However theuse of concentrated windings comes at a significant cost. Each phase ina concentrated winding machine requires separate input terminals,separate inverter output stages, separate wiring and fault detectioncircuitry, separate logic level PWM, and possibly separate current andvoltage measurement. Additionally, if the phase count is not sufficient,then a concentrated winding electrical machine does not make sufficientuse of its stator. The stator slots would be few and widely spaced.Concentrated winding induction machines are thus only useful when thephase count can be large.

The standard of industry for electrical rotating machines is thethree-phase system. Three phase systems cannot in general useconcentrated windings, with the exception of extremely high pole countsystems, in which the pole/phase group (PPG) might be limited to asingle slot. Rather, three phase systems use distributed and chordedwindings in order to make better use of the stator, and to eliminate thedeleterious results caused by non-synchronized components in the drivewaveform, winding flux distribution, or other sources of spatialharmonic magnetic fields.

In a stator with distributed windings, the series connected inductors ofa single phase are placed in a number of slots rather than in singleslot or slot pair. Inductors in the various slots somewhat counter themagnetic field produced by the series connected inductors in otherslots, reducing the effective current flowing in the inductors, and thusreducing the efficiency of producing a magnetic field. However thisreduction in magnetic field strength disproportionately effects harmonicmagnetic fields, the net result being that harmonic rotating fields arereduced, reducing low speed torque pulsation and torque cusp, as well asmaking better use of stator cross section given the low number ofphases.

FIG. 1 a (prior art) uses arrows to show the flux distribution in astator incorporating distributed windings, and FIG. 1 b uses arrows toshow the magnetic field strength in a stator incorporating concentratedwindings. A concentrated winding generates a field distribution that issquared. Physically, the field H (theta) is evenly distributed as shownin FIG. 1 b. In a distributed winding, the turns of the winding aredistributed so that the resultant field distribution is sinusoidal intheta, as depicted in FIG. 1 a.

FIG. 1 c shows the graph of a r=Hθ+baseline offset, the sinusoid whichthe distribution of the windings approximates as much as possible. Theideal approach is to distribute the turns according to the formuladN/dθ=(N/2)sin θ. That is, the turn density in number of turns perradian must be approximately (N/2)sin θ. The highest turn density willbe at ±π/2. The result of the sinusoidal distribution is to cancel, to avery large degree, all spatial harmonics.

Spatial and Temporal Harmonics

Spatial harmonics are regular distortions in the magnetic field producedin the stator of a rotating machine. Spatial harmonics with a pole countgreater than the pole count of the fundamental are filtered out and donot cause losses, if the windings of the stator are wound with a windingdistribution according to the sinusoid function.

Temporal harmonics, which originate with the drive waveform, arecurrents within the drive waveform that cycle faster than the drivewaveform. In a three phase machine, the magnetic fields that theseharmonics produce, if they were to be viewed in isolation, would havethe same number of poles as the fundamental, eg two poles in a two polemachine. This is because a three-phase machine does not fully sample thehigh frequencies of the temporal harmonics of the drive waveform. Thesetemporal harmonics therefore would produce a magnetic field in a threephase stator, which seems to be similar in shape to the fundamental andyet rotates faster than the fundamental around the stator, and often inthe reverse direction, depending on the specific harmonic involved. Thismagnetic field would not be filtered out by the windings being arrangedin a sinusoidal distribution, since they form a magnetic field with thesame number of poles as the fundamental, and the winding distributionfunction is only able to substantially affect magnetic fields of greaternumber of poles than the fundamental.

In a high phase order concentrated winding machine, all temporalharmonics with a harmonic number lower than the number of phases areproperly sampled, and produce on the stator a multi-pole rotatingmagnetic fields rotating with the same frequency and in the samedirection as the fundamental. These temporal harmonics, on the stator,directly become spatial harmonics. However, since they rotate at thesame speed and direction as the fundamental, they are desirable spatialharmonics, representing greater efficiency by causing extra beneficialtorque in the rotor.

Temporal harmonics with a higher harmonic number than the number ofphases will not be properly represented on the stator, and will producemagnetic fields with a number of poles different from double their phasenumber. For example, in a 17 phase 2-pole machine, the 19^(th) harmonicwould produce a 30-pole rotating field (15^(th) harmonic of 2 pole) andin a 7 phase, 4 pole machine, the 9^(th) harmonic would produce a 20pole rotating field (5^(th) harmonic of 4 pole). In a 7 phase 2-polemachine, the 13^(th) harmonic would be a 2-pole rotating field. In thecases when the harmonic order exceeds the number of phases, the rotatingfield produced by this harmonic will not be properly represented.Instead a rotating field that is a non-corresponding harmonic of thefundamental rotating field will be produced. This field may rotate at adifferent direction from the fundamental and possibly in the reversedirection This is similar to temporal harmonics with a harmonic numbergreater than three in a three phase machine, in the fact that theyrepresent detrimental torque. However, all the magnetic fields producedby these harmonics in the instances when the pole count is greater thanthe pole count of the fundamental, would be spatial harmonics of thefundamental, such as the 19^(th) harmonic in the 17 phase, 2 polemachine, which produces a 30 pole rotating field, and the 9^(th)harmonic in the 7 phase, 4 pole machine, which produces a 20 polerotating field.

Temporal harmonics that are even or are multiples of the number ofphases of the machine do not produce magnetic fields on the stator atall, due to symmetry and similar considerations.

Sampling and Reconstruction Filters

A bandwidth-limited continuous signal may be completely represented by adiscrete series of samples, providing that this series of samples occursfrequently enough. The continuous signal may have an amplitude whichchanges over time, in which case the samples form a time series ofmeasured amplitude versus integral time (e.g. 1 sample each second). Thecontinuous signal may be an amplitude which changes with position, inwhich case the samples for a series of measured amplitude versusintegral position, (e.g. 1 sample each meter). The period is arbitrary,and depends upon the signal being sampled. For baseband signals, thesampling frequency must be twice the maximum frequency present in thesignal being sampled, otherwise aliasing may occur. Aliasing is when thesignal being sampled contains frequency components that are outside ofthe allowed frequency range, in which case the results of sampling andreconstruction will be incorrectly produced, but allowed components.

Critical in the use of the sampling theorem is the use of thereconstruction filter. The reconstruction filter is a low pass filterthat recreates the intermediate values of the original continuous signalusing the data from the sample points. The winding of a motor isdistributed according to a reconstruction filter. The rotating currentstructures, and thus the rotating magnetic filed structures areexplicitly constrained by the form of the winding.

DISCLOSURE OF INVENTION

From the foregoing, it may be appreciated that a need has arisen for amore efficient rotating induction apparatus that filters out distortionssuch as spatial harmonics, but is nevertheless tolerant of desiredlow-order harmonics.

In one embodiment of the present invention an electrical rotatingmachine is connected with distributed windings, arranged according tothe sinc function. In a related embodiment, the electrical rotatingmachine is connected with distributed windings arranged according to acyclic analog of the sinc function.

In a further embodiment of the present invention, an electrical rotatingmachine is connected with distributed windings, arranged according toother low pass reconstruction filters.

It is an advantage of the present invention that an electrical rotatingmachine of more than three phases can be built that is able to useselected low order spatial harmonics but which filters out many higherorder spatial harmonics.

It is an advantage of the present invention that an electrical rotatingmachine can have electrically variable impedance. When a high phaseorder machine is connected with a mesh connection to the inverter drive,then low-order harmonics added to the waveform can significantly changethe impedance of the machine. At the same time, higher-order spatialharmonics that are less useful and often detrimental, are filtered outof the machine.

It is an advantage of the present invention that the same electricalrotating machine can be used for both high speed and tractionapplications.

It is an advantage of the present invention that the drive circuitry maybe economically produced.

BRIEF DESCRIPTION OF DRAWINGS

For a more complete explanation of the present invention and thetechnical advantages thereof, reference is now made to the followingdescription and the accompanying drawings, in which:

FIG. 1 a shows a stator with concentrated windings (prior art).

FIG. 1 b shows a stator with distributed windings according to asinusoidal distribution (prior art).

FIG. 1 c shows a sinusoid, which the distributed windings of FIG. 1 b.attempts to approximate.

FIG. 2 shows a sinc function.

FIG. 3 shows the Ideal Lowpass Filter Frequency Response.

FIG. 4 shows a plurality of adjacent sinc functions linearly displayed.

FIG. 5 shows the sinc function with a cutoff frequency of pi.

FIG. 6 shows a further graph of the sinc function.

FIG. 7 shows the winding distribution according to the cyclic sincfunction of a 30 slot machine, with a cutoff at the fundamental.

FIG. 8 shows the winding distribution according to the cyclic sincfunction of a 30 slot machine, with a cutoff at the 3^(rd) harmonic.

FIG. 9 shows the winding distribution according to the cyclic sincfunction of a 30 slot machine, with a cutoff at the 5^(th) harmonic.

FIG. 10 shows the winding distribution according to the cyclic sincfunction of a 30 slot machine, with a cutoff at the 7^(th) harmonic.

FIG. 11 shows the winding distribution according to the cyclic sincfunction of a 30 slot machine, with a cutoff at the 9^(th) harmonic.

FIG. 12 shows the winding distribution according to the cyclic sincfunction of a 30 slot machine, with a cutoff at the 11^(th) harmonic.

FIG. 13 shows the winding distribution according to the cyclic sincfunction of a 30 slot machine, with a cutoff at the 13^(th) harmonic.

FIG. 14 shows the winding distribution according to the cyclic sincfunction of a 30 slot machine, with a cutoff at the 3^(rd) harmonic.

FIG. 15 shows the winding distribution according to the cyclic sincfunction of a 36 slot machine, 9-phase machine, with a cutoff at the3^(rd) harmonic.

FIG. 16 shows the winding distribution according to the cyclic sincfunction of a 36 slot machine, 12-phase machine, with a cutoff at the3^(rd) harmonic.

FIG. 17 shows a rotating electrical machine with more than three phases,(eight), star connected to an equal number of inverter terminals(represented by circles 5) providing multiple phases of drive waveform.

FIG. 18 shows a rotating electrical machine with more than three phases,(eight), mesh connected to an equal number of inverter terminals(represented by circles 5) providing multiple phases of drive waveform.

BEST MODE FOR CARRYING OUT THE INVENTION

The current flowing in the stator slots produces the rotating magneticfield of an electrical rotating machine. This current flow changes overtime, causing the overall structure of the stator current distributionto change over time and rotate. In the ideal case, the stator currentdistribution is fixed in shape, but simply rotating. The various phasesfeeding the motor can be thought of as spatially sampling this currentdistribution, and the physically distributed turns of winding in thestator can be thought of as the necessary reconstruction filter. Eachphase describes the current flowing at one location in each pole of thestator, and the winding distribution acts to smooth out this currentflow appropriately.

Spatial harmonics, or air-gap harmonics, are harmonic fields generatedby the non-sinusoidal nature of the field generated by each winding.When spatial harmonics are excited by the fundamental drive currents,they produce a secondary rotating field that rotates slower than thefundamental field. For a given excitation frequency, spatial harmonicfields rotate more slowly than the fundamental field.

Harmonic fields generated by non-sinusoidal drive wave-forms are termedtemporal harmonics. Rotating fields produced by temporal harmoniccurrents rotate more rapidly than the fundamental field. When temporalharmonics excite the fundamental spatial field, they produce a secondaryrotating field that rotates more rapidly than the fundamental field andmay rotate in the opposite direction to the fundamental field.

The idealized winding distribution used in three phase machines is thesinusoidal distribution, in which the number of inductors in each slotfor each phase is proportional to the sine of the angle of that slotfrom a reference zero. Each phase has its own reference zero, and in athree-phase system the various phases are all 120 electrical degreesapart. In real windings, various greatly simplified windings are used,which variously use distributed sets of coils, each with the same numberof turns, and short pitch coils, which do not reach to the next pole, inorder to produce distributions of inductors which reasonably approximatethe ideal sinusoidal distribution.

In the present invention, a high phase order induction machine, havingmore than three phases, is wound using distributed windings. Instead ofusing the sine function necessarily as the distribution function, adistribution function is selected so as to permit only the desiredtemporal harmonics to produce the rotating magnetic field. All otherspatial harmonics (including those that originated as temporalharmonics), are canceled, or filtered out, or mitigated, as in thefashion of those spatial harmonics in the three-phase system withsinusoidal distributed windings.

The desired temporal harmonics are the fundamental and specific loworder harmonics. For example, it may be desirable to use and even addthird and fifth temporal harmonics in a high phase order machine,especially if the machine is mesh connected, as described below.Therefore these together with the fundamental would be the desiredharmonics. All other spatial harmonics would be cancelled, eliminatingboth those that could produce useful torque such as those thatoriginated as temporal harmonics, having a harmonic number lower thanthe number of phases, as well as all detrimental spatial harmonicsgreater than the fifth.

The desired reconstruction filter will thus be a low pass filter. Thereconstruction filter is implemented by selecting the appropriate numberof inductors in each slot that are connected electrically in series toform each phase. This number of inductors can be written as a functionof desired cutoff frequency (C) and slot position (S). The simplest lowpass filter used is the sinc function, well known in the field ofdigital audio where sampling is frequently used. The sinc function issimply sin(f*x)/(f*x), where f is the cutoff frequency, normalized sothat with a cutoff frequency of 1, the first zero of the basic sincfunction will be 90*N electrical degrees from the peak of the sincfunction, where N is any integer.

For purposes of producing a suitable winding distribution, which must beconfined to a finite stator, and must respect symmetries inherent in theactual windings themselves, the sinc function is modified by adding toit a negative version of itself, offset by 180 electrical degrees.

In order to calculate the cyclic function for use in determining thenumber of turns for each phase that should be placed in each slot, thefollowing formula (in radians) is used:Cyclic sinc(S)=Σ{−n+}, (sinc(C*y)−sinc(C*y−π)

where y=S+πn

${{Cyclic}\mspace{14mu}\sin\;{c(S)}} = {\sum\limits_{n = {- \infty}}^{+ \infty}\;\left\{ {{\sin\;{c\left( {C\left( {S + {2\;\pi\; n}} \right)} \right)}} - {\sin\;{c\left( {{C\left( {S + {2\;\pi\; n}} \right)} - \pi} \right)}}} \right\}}$where C is the cutoff harmonic, S is the slot angle in radians, from thereference zero of the phase, and n is an integer between from negativeinfinity and positive infinity.

This function would result in a distribution centered around the zerodegrees slot. For each phase it should therefore be rotated around thestator by the phase angle (P). The phase angle P, in radians, would be2π/((phases)*(poles)).

The results of the distribution for various slots would be scaled by thetotal number of effective series turns required by machine voltage andpole area, as is well known in three phase machines for dealing withdistribution or chording.

Furthermore, in a conventional three phase distributed winding machine,the ideal sinusoidal distribution is approximated by practical physicalwindings which are constrained by issues such as requiring full coilturns in a winding, or the desire to use coils all of the same turncount. Similarly, in the present invention, the ideal low pass filterdistribution functions may simply be approximated in a similar fashion.

One useful approximation would be to only consider the broad centralregion of the sinc function and distribute the windings for each phaseonly within this broad region (and its inverse, on the other side of thestator, while ignoring the other regions. In a second usefulapproximation one would not even consider the differences between theincrements within the broad central region, treating the region with asinusoidal distribution. In a third useful approximation the broadcentral region would be considered as a straight slope. In a fourthuseful approximation, one would consider only the broad central positiveregion and the smaller negative lobes to either side of it, and ofcourse, in all the approximations, also the inverses of these on theother side of the stator.

For the fourth useful approximation, a cyclic sinc winding distributionwith a cutoff at the third harmonic is described. The trend of this sincfunction may be determined as having two different degrees ofincrements, that of 4 units and that of 1 unit. Within the broad centrallobe, the function starts with a slot containing zero turns of windings,then the number of turns increases by about 4 units per slot until thetopmost region, then there is usually one slot containing an incrementof 1 unit to reach the maximum number of turns, a single slot containinga decrement of 1 unit, and then the function decreases again withdecrements of 4 units to reach a slot containing zero turns of windingagain. The total number of slots containing windings in this broadcentral region is just under two thirds of the total number of slots perpole of the machine, for example, 11 in a 36 slot machine and 9 in a 30slot machine. On each of the further sides of the two slots containingzero turns, there are two slots (or more, depending on the number ofslots in the machine), with approximately the same number of turns in,one unit decrement below zero. The next slot once again contains zeroturns.

In a further approximation, windings with the same total number of turnsare positioned so that they approximate the ideal cyclic sinc functionby having roughly the same total number of turns centered in each lobeof the function.

In the first approximation mentioned above, the 11 or 9 slots (adjustedfor machines with different numbers of slots) of the broad centralregion, would be the only ones to contain windings for each phase. Inthe second approximation above the turns would be distributedsinusoidically throughout these slots, and in the third approximationthere would be a gradient of increasing number of turns, reaching themaximum number of turns and then a declining gradient reaching zeroturns again.

In one embodiment, the electrical rotating machine is a 5-phase machine.A (sin fx)/fx winding distribution is selected such that the winding ofeach phase has zero amplitude at the central point of each adjacentphase (in other words, the points on the stator where the windingdistribution has zero turns are placed at multiples of 36 electricaldegrees from the center of the pole/phase group (PPG)), producing awinding which has it's ‘desired spatial cutoff frequency’ at the 5thharmonic. The total number of series turns is selected usingconventional distributed winding calculation techniques so as to providea proper winding voltage at the desired flux density and drivefrequency. In another way of describing the same idea, the cyclic sincfunction described above is used, in which the cutoff frequency C=5 andfor each slot angle S in radians from a reference point for each phase,the winding distribution of S is calculated using the formula

$\begin{matrix}{{{cyclic}\mspace{14mu}{sinc}\mspace{14mu}(S)} = {{\left( {\sin\left( {5*\left( {S + {2\pi\; n}} \right)} \right)} \right)/\left( {5*\left( {S + {2\pi\; n}} \right)} \right)} -}} \\{\left( {\sin\left( {{5*\left( {S + {2\pi\; n}} \right)} - p} \right)} \right)/\left( {{5*\left( {S + {2\pi\; n}} \right)} - \pi} \right)} \\{= {\left( {{\sin\left( {{5S} + {10\pi\; n}} \right)}/\left( {{5S} + {10\pi\; n}} \right)} \right) -}} \\{\left( {{\sin\left( {{5S} + {10\pi\; n} - \pi} \right)}/\left( {{5S} + {10\pi\; n} - \pi} \right)} \right)}\end{matrix}$

For each slot, the angle in radians S from a keystone physical angle onthe stator may be substituted into the above equation, to produce aresult from the above equation determining the number of turns thatshould ideally be placed in that slot. For example, if the number ofturns of winding for a keystone slot itself were to be determined, S=0and the result of the formula would be 1.

A graph of the number of winding turns in each slot of a 30 slotmachine, may be seen in FIG. 9. Various other graphs of windingdistributions in machines with different numbers of slots and withcutoff frequencies at different harmonics may be seen in FIGS. 7–16.

In another embodiment, a second possible winding configuration for the5-phase machine is described. The cyclic sinc function described aboveis used with the cutoff harmonic C set to 4, for the fourth harmonic, toallow the third spatial harmonic to flow, but prevent the fifth andhigher spatial harmonics from flowing. The fifth harmonic actually doesnot usually enter the five-phase machine, just as the third harmonicdoes not enter the three-phase machine. The fourth harmonic also doesnot normally flow, due to symmetry within the machine. However, if thecutoff harmonic were one that could enter the machine, it would bepartially filtered and partially allowed to flow.

In another way of describing the same winding distribution, a sincfunction (sin fx)/fx winding distribution is selected to place its zerosat multiples of 45 degrees from the center of the pole/phase group,creating a reconstruction filter with a cutoff at the fourth harmonic,passing the third harmonic without attenuation, but eliminating 7th andhigher harmonic torque cusps. “Placing the zeros” of the sinc functionat 45 degrees, is another way of saying that for 45 degrees in bothdirections, from a keystone angle on the stator for each phase, there isbe a broad central region of gradually decreasing numbers of turns ofwindings. At 45 degrees away from the keystone slot, there would be nowindings at all, and after that the number of turns of windings wouldincrease again, but would be placed in the opposite direction going downthe stator instead of up the stator. Theoretically, every 45 degrees thenumber of turns would again decline to zero, after which the directionof the windings would change, but in effect the function also takes intoconsideration the exact opposite configuration which must take place 180degrees to the other side of the stator, and some of the turn incrementsand decrements would cancel one another out, which is why the cyclicsinc function described above would need to be used to determine moreaccurately the number of winding turns in each slot, or approximationstherefore. Furthermore, there are a limited number of times 45 degreesaway from a keystone slot appears on a stator.

In a further embodiment of the present invention, the third harmonic isinjected into the motor at low speeds, thus appearing as a 6-polerotating field in the nominally 2 pole motor frame. Furthermore, thewindings of the motor are connected in a mesh connection, (as opposed toa star connection), and therefore the current seen within the windingcan be much higher than the current injected from the drive. The drive,which has substantial low speed voltage available, but limited current,is thus able to provide much higher torques at low speeds than a motorwhich is not specifically fed a harmonic. The winding distribution wouldbe a sinc function with a cutoff at the fourth or fifth harmonic, toallow the third spatial harmonic to pass, but not higher spatialharmonics. In a five-phase machine, the third temporal harmonic becomesthe third spatial harmonic and would not be filtered out by this windingdistribution.

In a further embodiment of the present invention, a seven phaseelectrical rotating machine is used, and a low pass reconstructionfilter is used to determine the winding distribution, with a functionf(x) selected to allow the third and the fifth harmonics to be used inthe machine, whilst filtering out higher order harmonics to a greatextent. The low pass filter may be the sinc function, or other low passfilter capable of allowing substantially only the third and fifthharmonics to pass. A graph showing the distribution of the sinc functionin a motor with a cutoff frequency at the seventh harmonic is shown inFIG. 10. The distribution of the windings is independent of the numberof phases in the machine and depends only on the number of slots, exceptthat it will be repeated according to the number of and positions of thephases, and may be scaled accordingly.

In a further embodiment, a nine phase electrical rotating machine isused, and a low pass reconstruction filter is used to determine thewinding distribution, to filter out most harmonics and only allow entryto the machine of spatial harmonics below the ninth. This may be seen inFIG. xxx.

In a further embodiment, electrical rotating machines with higher phasecounts are used, with a reconstruction filter used to determine thewinding distribution to substantially filter out harmonics having aharmonic number lower than the number of phases. This may be seen inFIG. 13 with reference to a fifteen-phase machine, having a cutofffrequency at the thirteenth harmonic. However, it is desirable thatelectrical rotating machines with high phase counts should be used inmachines with more than double the number of slots as phases, since forexample in a 30 slot, 15 phase machine, the winding approximates aconcentrated winding.

In a further embodiment, the electrical rotating machine is connectedwith a mesh connection to the inverter drive. In this way, the voltageacross each winding is actually a function of the two different voltagesplaced at the two ends of the same winding, and thus may besubstantially different from any of the voltages produced at that timeby the inverter. Voltages may therefore be much higher in the windingsthan were actually generated by the inverter drive, and currents may bemuch lower, or alternatively, currents may be greatly increased whilstvoltages are reduced. A mesh connection is depicted in FIG. 18. Thisexample shows a mesh connection in which both ends of each motor phasewinding are connected to adjacent inverter terminal outputs. In otherwords, it has a span value of L=1. However, the mesh may be arrangedthat both ends of each motor winding phase be connected to span agreater number of inverter terminal outputs. For example, if both endsof each motor winding phase would be connected to inverter terminalsalmost but not exactly 120 electrical degrees out of phase from eachother, then the injection of third harmonic into the electrical currentof the drive waveform would have a significant effect on the current tovoltage ratio of the electrical rotating machine, and hence, on thetorque and speed of the output of the electrical rotating machine. In afive phase machine, the L=2 connection connects each motor winding phaseto inverter terminals 144 degrees apart. In contrast to a meshconnection, FIG. 17 shows an eight-phase machine connected to inverterterminals with a star connection.

In a further embodiment, the inverter logic may be configured to injecta pure harmonic drive waveform, for example, pure third or pure fifthharmonic. Due to the mesh connection, this pure harmonic drive waveformwould significantly change the voltage across each winding, allowingvery high voltages to be reached in the windings, or very high speeds.The mesh connection may be initially set up or switchable so that itcreates a very large change in current/voltage ratios, when switchedbetween fundamental and an injection of pure third harmonic or purefifth harmonic drive waveform.

In a further embodiment, a harmonic can be supplied to the electricalrotating machine simultaneously to a fundamental pole count drivewaveform. In one embodiment, a fundamental drive waveform employs atwo-pole rotating field. Superimposed to a selective degree to this canbe the third harmonic. This effectively changes the voltage across thewinding, and the currents going through the machine. Therefore, theaddition of harmonics in this way, may electrically vary the impedanceof the machine.

Certain mesh connections, such as those in which the two ends of eachwinding are connected to two inverter outputs with an electrical angledifference of approximately but not exactly 120 electrical degrees, areable to take particular advantage of the injection of third harmonic, toproduce large changes in impedance.

In a further embodiment, fifth harmonic may be injected into the drivewaveform, to further provide impedance variation. The fifth harmonic maybe used simultaneously or separately from the third harmonic, and may besuperimposed onto or used instead of the fundamental. In addition, themesh connection used may be one that uses fifth harmonic to the bestadvantage, as detailed in my other patent application.

In a further embodiment, a winding distribution may be set up thatallows many low-order harmonics, those below the phase count, to allflow in the machine, such as a 15 phase machine with a cutoff frequencyat the thirteenth harmonic. These low-order harmonics may be selectivelyadded to provide further or alternative variance in impedance.

It will be understood that various control logic circuitry, well knownin the art, may be employed to determine when extra voltage or extracurrent is required from the machine. These control logic circuitrycomponents would be connected to automatically add or eliminate extraharmonics according to these requirements. This would have the effect oftemporarily boosting voltage across each winding whilst reducing themaximum current able to flow through the windings, or temporarilyboosting the current through the windings whilst reducing the maximumvoltage possible across the windings. The voltage across the windings isdirectly related to the output speed of the machine and the currentsthrough the windings are directly related to the output torque of themachine.

A user input may also be incorporated to allow manual control over thecurrent/voltage ratio. This is also known as the impedance of themachine.

In a further embodiment, the mesh connection is specifically designed tomake the best use of the low order harmonics that are able to flow inthe electrical rotating machine. This is described in great detail in myU.S. Pat. No. 6,657,334. Usually, the third harmonic is able to producethe greatest variability between currents and voltages across windings.

A preferred embodiment uses a five phase machine, with a sinc functionfilter used to describe a distribution that allows third harmonic toflow in the machine whilst filtering out all other harmonics, having acutoff frequency C set to 4. The five phases comprise a mesh connectionwith the two ends of each winding connected to inverter terminals 144electrical degrees apart, in other words, having a span of L=2. Theinverter drive supplies fundamental waveform current with a variableamount of added third harmonic component.

1. A high phase order rotating induction machine, comprising a statorhaving windings for each of said phases, the number of phases is greaterthan three, a number of inductors is a function of desired cutofffrequency and slot position, said windings are distributed according toa sinc function or an approximation of a sinc function:sinc=sin(f*x)/(f*x) where sinc is the cutoff harmonic, and f is thecutoff frequency, normalized so that at a cut of frequency of 1, thefirst zero of the sinc function will be 90*N electrical degrees frompeak of the sinc function, where N is any integer between negativeinfinity and positive infinity, such that a suitable windingdistribution is formed centered around a zero degree reference slot. 2.The rotating induction machine of claim 1 wherein said windings aredistributed according to an approximation of a sine function.
 3. Therotating induction machine of claim 2 wherein said sine function has acutoff frequency at a fourth or a fifth harmonic.
 4. The rotatinginduction machine of claim 2 wherein the number of phases is five andwherein said sine function has a cutoff frequency at a third spatialharmonic.
 5. The rotating induction machine of claim 4 furthercomprising a high phase inverter drive, wherein the number of phases isthe same as the number of phases of said rotating induction machine,electrically connected to said windings, wherein said windings areconnected to said inverter drive wit a mesh connection.
 6. The rotatinginduction machine of claim 5 wherein said inverter drive is capable ofselectively injecting third harmonic into a drive waveform, and whereinsaid mesh connection has a span of L=2.
 7. A high phase order rotatinginduction machine, comprising a stator having windings for each of saidphases, the number of chases is greater than three, said windings aredistributed according to a cyclic sinc function or an approximation of acyclic sinc function:${{cyclic}\mspace{14mu}\sin\;{c(S)}} = {\sum\limits_{n = {- \infty}}^{+ \infty}\;\left\{ {{\sin\;{c\left( {C\left( {S + {2\;\pi\; n}} \right)} \right)}} - {\sin\;{c\left( {{C\left( {S + {2\;\pi\; n}} \right)} - \pi} \right)}}} \right\}}$where C is the cutoff harmonic, S is the slot angle in radians, from thereference zero of the phase, and n is an integer between from negativeinfinity and positive infinity, such that a suitable windingdistribution is formed centered around a zero degree reference slot. 8.The rotating induction machine of claim 7 wherein said windings aredistributed according to an approximation of a cyclic sinc function. 9.The rotating induction machine of claim 8 wherein said cyclic functionhas a cutoff frequency to pass low-order harmonics and to substantiallyfilter out all higher harmonics.
 10. The rotating induction machine ofclaim 8 wherein said windings are distributed to give a fixed number ofturns positioned in the center of each lobe of the cyclic sinc function.11. The rotating induction machine of claim 10 wherein said cyclicfunction has a cutoff frequency to pass low order harmonics and tosubstantially filter out high-order harmonics.
 12. The rotatinginduction machine of claim 8 additionally comprising groups of windingpositioned in a single lobe on either side of said central lobe.
 13. Therotating induction machine of claim 8 wherein said cyclic sinc functionhas a cutoff frequency at the fourth or the fifth harmonic.
 14. Therotating induction machine of claim 8 wherein the number of phases isfive and wherein said sine function has a cutoff frequency at a thirdspatial harmonic.
 15. The rotating induction machine of claim 14 furthercomprising a high phase inverter drive, wherein the number of phases isthe same as the number of phases of said rotating induction machine,electrically connected to said windings, wherein said windings areconnected to said inverter drive with a mesh connection.
 16. Therotating induction machine of claim 14 wherein said mesh connection hasa span of L=2.
 17. The rotating induction machine of claim 8 furthercomprising a high phase inverter drive, wherein the number of phases isthe same as the number of phases of said rotating induction machine,electrically connected to said windings, wherein said windings areconnected to said inverter drive with a mesh connection and wherein saidinverter drive is capable of selectively injecting low order harmonicsinto a drive waveform.
 18. The rotating induction machine of claim 17wherein said cyclic sine function has a cutoff frequency to pass saidlow order harmonics only.
 19. The rotating induction machine of claim 8wherein said windings are distributed for each phase to approximate onlythe broad central regions of the cyclic sine function, ignoring the sidelobes of the cyclic sine function.
 20. The rotating induction machine ofclaim 19 wherein within said broad central region said windings aredistributed to approximate a sine function.
 21. The rotating inductionmachine of claim 19 wherein within said broad central region saidwindings are distributed to approximate the cyclic sinc function with agradient of increasing number of turns up to a maximum value.